KR910004700B1 - Aromatic polyamide short fibers and its manufacturing method - Google Patents

Abstract

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Description

Aromatic polyamide short fibers and its manufacturing method

1 is a schematic diagram of a device used in the present invention,

2 is a cross-sectional view of the rotating tube cut in the direction perpendicular to the axis of rotation.

* Explanation of symbols for main parts of the drawings

1: liquid crystal prepolymer input 2: hole

3: rotating tube 4: motor

5: rotating shaft 6: nozzle

7: overflow line 8: injection part of polymerization promoter

9: General container 10: Center of rotation axis

The present invention relates to an aromatic polyamide short fiber and a method for manufacturing the same, and particularly, an aromatic polyamide stage having excellent physical properties and molecular orientation produced using a novel apparatus capable of easily changing the length and molecular orientation angle of the fiber. A fiber and a method for producing the same.

Conventionally, when preparing aromatic polyamide short fibers as described in US Pat. No. 3,429,293 and US Pat. No. 3869430, the polymer is washed with water after polymerization of an inorganic salt, an aromatic diamine and an aromatic dieside chloride in an amide solvent. After drying, the mixture was dissolved in more than 98% sulfuric acid solvent to form a dope, and the dope was spun into water through a nozzle to obtain a fiber. The fiber was then cut or pulverized to prepare a short fiber. However, this manufacturing method requires a multi-step process of separating, washing with water, drying and dissolving the polymer in a sulfuric acid solvent and spinning it, thus increasing the manufacturing cost and corroding the manufacturing apparatus during the process due to the use of a sulfuric acid solvent. Problems appeared.

On the other hand, U.S. Patent No. 4511623 describes a method for preparing aromatic polyamide short fibers by precipitating a prepolymer polymerized in an amide solvent having an inorganic salt in direct water or an amide solution and applying shear force. . However, since this method is similar to the wet spinning method by imparting shear force in a solvent, the fiber can be developed in the process of manufacturing short fibers, but it is difficult to improve the physical properties. There was a problem that it is difficult to manufacture continuously because time is required.

In addition, in Korean Patent No. 25542, a liquid crystal prepolymer of an aromatic polyamide is extruded from the outside of the tube to the inside of the tube through a nozzle, and at the same time, the polymerization accelerator precipitates are injected into the tube to increase the velocity of the polymerization precipitate in the tube. A method for producing pulp short fibers is disclosed. However, this method is also the same as the wet spinning method where polymerization occurs in the place where the air layer is not formed, and it is difficult to improve the physical properties, and the direction of the nozzle through which the liquid crystal prepolymer passes, that is, the flow direction of the liquid crystal prepolymer and the polymerization accelerator. Since the prepolymer is supplied in a state in which the direction of is perpendicular, it is difficult to achieve a desirable molecular alignment state by causing interference with the molecular alignment of the fiber. Accordingly, the present inventors have studied various methods to improve the problems described above, by providing an elongation to the prepolymer to easily change the length and molecular orientation angle of the fiber to produce a short fiber excellent in molecular orientation I developed a method.

Accordingly, an object of the present invention is to provide an aromatic polyamide short fiber having excellent physical properties and molecular orientation at low cost by using a novel apparatus having a simple process in producing an aromatic polyamide short fiber.

Hereinafter, the present invention will be described in detail.

The present invention is optically anisotropic obtained by dissolving an inorganic salt in an amide solvent or an amide solvent containing a small amount of tertiary amine and polymerizing at low temperature by adding an equimolar amount of aromatic diamine and aromatic dieside chloride. Alternatively, the anisotropic liquid crystal prepolymer is supplied to the nozzle formed in the container by using a gear pump and sprayed to prepare aromatic polyamide short fibers, and the nozzle itself is rotated to draw the liquid crystal prepolymer passing through the nozzle. In order to facilitate molecular orientation, the liquid crystal prepolymer has a greater centrifugal force due to rotation than the speed of passage through the nozzle so that the ratio of the centrifugal force and the prepolymer force when passing through the nozzle is 10 or more. The liquid crystal prepolymer injected from the air layer formed in the To a stretching method for the preparation of aromatic polyamide monofilament which comes into contact with a polymerization promoting precipitation solvent to be immersed is achieved As the aromatic polyamide as end doemeurosseo polymer molecular weight is increased by the short fibers is prepared and then made.

Short fibers as the final polymer have a fully extended molecular chain structure, the chain end distribution is uniformly distributed in the fiber axis direction, there is no kink band due to the crystal defect layer and the corrugated sheet structure in the fiber axis direction It is characterized by an aromatic polyamide short fiber having a uniform structure with a uniform fiber length, having a draw ratio of 1.0 or more, an intrinsic viscosity of 3.0 or more, and a molecular orientation angle of 21 or less.

Such a present invention will be described in more detail as follows.

When the inorganic salt is added to the amide solvent, the present invention adds and dissolves 0.5 to 15% by weight with respect to the polymerization solvent, and polymerizes an equimolar amount of aromatic diamine and aromatic dieside chloride at a low temperature of 40 ° C or lower, thereby intrinsic viscosity. Is 0.8 to 3.5, and an optically anisotropic or anisotropic liquid crystal prepolymer having a repeating unit consisting of the following structural formulas (A) or (B) is prepared and then sprayed through a spray nozzle, and the stretching ratio is 1.0 or more by rotating the spray nozzle. The polymerization is carried out at a low temperature of 50 ° C. or less. In this case, as the polymerization accelerator, a solvent containing tertiary amine alone or a mixed solvent in which tertiary amine and amide solvent are mixed or a small amount of inorganic salt is used.

Provided that R ₁ , R ₂ and R ₃ are as follows.

X = H, C1, Br, I, R₁ and R₂ may be same or different, and R₁ and R₂ are generally present in equimolar amounts.

In addition, the intrinsic viscosity of the above-mentioned final polymer was calculated | required from the following relationship.

Intrinsic Viscosity = 1n (ηrel) / C

Where C is the concentration of the polymerization solution and η _rel is the flow time ratio between the solution and the solvent in a capillary viscometer maintained at 30 ° C as relative viscosity.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

When an optically anisotropic or anisotropic liquid crystalline prepolymer having a viscosity of 5 to 100,000 poise is quantitatively supplied to the liquid crystal prepolymer inlet 1 of the device according to the present invention by using a gear pump, the liquid crystal prepolymer provides a hole (2). Therefore, the liquid crystal prepolymer introduced into the rotary tube 3 and introduced into the rotary tube 3 while the rotary shaft 5 is rotated by the motor 4 is injected through the nozzle 6. At this time, the upper and lower limits of the nozzle 6 may be introduced in the range of the overflow line 7 or less and the polymerization inlet for injection acceleration 8 or more. The solvent in the polymerization vessel (9) causes a swirling phenomenon as the rotary tube (3) rotates, forming an air layer between the nozzle (6) and the solvent, and the injected liquid crystal prepolymer is stretched. The final polymer is made by the precipitation solvent added through.

In the polymerization vessel 9, the slurry is discharged through the overflow line 7 while the vortex is maintained in the slurry state in which the pulp-like short fibers are suspended.

However, due to the low speed rotation, the vortex phenomenon in the polymerization vessel is small, and when the air layer is not formed between the nozzle and the precipitation solvent, short fibers are formed but the physical properties are not good.

The nozzle in this device is arranged in the tube in parallel with the direction of the longitudinal direction of the tube and the rotation axis, the shape of the nozzle is not particularly limited, but the most suitable circular. The diameter of the circular nozzle may be 0.01 to 5.0mm, preferably 0.05 to 1.0mm. The ratio (L / D) of the length to the diameter of the nozzle is preferably in the range of 1 to 10.

In addition, the nozzle installation method, as shown in (a) and (b) of FIG. 2, is installed in the entire circumference of the tube or in the 180 ° range by the rotation axis center method (10), the discharge direction of the liquid crystal prepolymer The direction of the centrifugal force is reversed and the stretching effect cannot be obtained. Even when discharged, the orientation angle of the short fibers is 37 ° or more, so that the molecular orientation is not achieved. However, as shown in (c) and (d) of FIG. 2, when the nozzles are arranged in the range of 180 ° in the direction opposite to the center of the rotation axis, the direction in which the liquid crystal prepolymer passes through the nozzle and the direction in which the centrifugal force acts are similar to each other. Among them, as shown in (d), the shape of the array has a narrow angle with respect to the direction of the rotational center may have a greater effect.

As such, the liquid crystal prepolymer is stretched due to the centrifugal force generated by the rotation of the nozzle. The factor controlling the draw ratio is the centrifugal force determined by the rotational angular velocity (ω) and the distance from the rotation center to the nozzle (r). It is the ratio of the force (Fp) received by the liquid crystal prepolymer through the nozzle by (Fr) and the gear pump. The ratio of Fr and Fp can be adjusted to 1.0 or more, but if the ratio is less than 10, the air layer is not formed due to the vortex phenomenon inside the polymerization vessel, so that the physical properties of the final polymer are not good. The distance from the center of rotation axis to the nozzle is adjustable from 10 to 500 mm, preferably from 50 to 350 mm.

According to the present invention, various effects can be obtained, and among them, a wide range of prepolymers (viscosity range of 5 to 100,000 poise) can be used, which can be applied to liquid crystal polymers of various aromatic polyamides, and the number, size and inlet of nozzles. Production can be controlled by size and the physical properties such as tensile strength are excellent because the centrifugal force generated by the rotating tube not only makes it easy to disperse the prepolymer in the nozzle, but also the stretching by the centrifugal force is carried out in the air. Because of the excellent molecular orientation of the prepared short fibers, the pulp can be easily produced by a simple grinding method, and the length of the short fibers can be reduced by controlling the ratio of the spraying speed and the centrifugal force by the rotation. Of polystyrene pulp-like short fibers It is possible to obtain a variety of effects, such as possible.

Hereinafter will be described in more detail based on the embodiment of the present invention.

Example 1

The reaction tank was thoroughly purged with nitrogen to completely remove water, and 500 ml of N-methyl-2-pyrrolidone was added thereto as an amide solvent. The temperature was raised to 80 ° C., and the metal halide salt was dissolved. Thus, 207.6 g of p-phenylenediamine was added to the amide-based polymerization solvent in which the inorganic salt was dissolved, and the mixture was dissolved while stirring for 10 minutes. 391.6 g of terephthaloyl chloride was added at a low temperature of 30 ° C. or lower, followed by vigorous stirring. After 8 minutes, the stirring was stopped and the obtained liquid crystal prepolymer was supplied to the liquid crystal prepolymer inlet portion of the apparatus of the present invention by using a gear pump in a polymerization vessel.

In this case, the ratio of centrifugal force (Fr) due to tube rotation and the force (Fp) received by the liquid crystal prepolymer during the passage of the nozzle was changed and measured at 10 or more. The arrangement of the nozzles used the arrangement method as shown in FIG. Physical properties of the obtained pulp-like short fibers are as shown in Table 1.

Comparative Example 1

After the polymerization as described above, when the liquid crystal prepolymer was introduced into the nozzle, the ratio of Fr and Fp was measured as 1, 4 and 8, and the physical properties of the pulp-like short fibers obtained at this time are shown in Table 1. When the value of Fr / Fp is 10 or less, it can be seen that the physical properties decrease.

TABLE 1

Example 2

In the same manner as in Example 1, but changing the arrangement of the nozzle as shown in Figure 2, the physical properties of the prepared short fibers were measured and the results are shown in Table 2.

The physical properties of the short fibers by the arrangement of (d) were the best, but in order to manufacture more products, the arrangement of (c) was found to be good.

TABLE 2

Claims (3)

Optical anisotropy or anisotropy obtained by adding an inorganic salt to an amide solvent containing an amide solvent or a small amount of tertiary amine and dissolving the same, and then adding an equimolar amount of aromatic diamine and an aromatic dieside chloride to polymerize at low temperature. In preparing the aromatic polyamide short fibers by supplying and spraying the liquid crystal prepolymer as a nozzle installed in the container by using a gear pump, the nozzle itself is rotated so as to stretch the aromatic polyamide prepolymer exiting the nozzle. The centrifugal force of the prepolymer is greater than the speed at which the prepolymer passes through the nozzle so that the dispersion direction can be easily achieved, so that the ratio of the centrifugal force and the prepolymer force when passing through the nozzle is 10 or more, and the air layer formed between the nozzle and the precipitation solvent Liquid crystal prepolymer injected from After stretching is carried out by, the method for producing an aromatic polyamide short fiber characterized in that the molecular weight is increased while being immersed in contact with the polymerization promoter for immersion. Aromatic polyamide short fibers, which have a fully extended molecular chain structure, whose chain end distribution is uniformly distributed in the fiber axis direction, and in the fiber side direction, there are kink bands according to the crystal bonding layer and the corrugated sheet structure. Aromatic polyamide short fibers, characterized in that it has a single structure having a draw ratio of 1.0 or more, an intrinsic viscosity of 300 or less, and a molecular orientation angle of 21 degrees or less, and a uniform fiber length distribution. The method of claim 1, wherein the nozzle arrangement is arranged in the range of 180 degrees in the direction opposite to the center of the rotation axis, so that the direction in which the liquid crystal prepolymer passes through the nozzle and the direction in which the centrifugal force acts are similar to obtain the stretching effect by the centrifugal force. Method for producing an aromatic polyamide short fibers, characterized in that.

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